BI105A Environmental Biology

1. BI105AEnvironmental Biology Professor Jill Nissen Montgomery College Fall 2006

2. Chapter 3 Ecosystems and Energy

3. Ecology • The study of interactions among organisms, and between organisms and their abiotic environment • Ecologists study the highest levels of biological organization that include or are above the individual organism: • Population • Community • Ecosystem • Landscape • Biosphere

4. Levels of Biological Organization Population = A group of individuals of the same species occupying the same area at the same time Community = An association of populations that are tired together directly or indirectly by competition for resources, predation, and other interactions Ecosystem = A complex of organisms and their physical environment, linked by a recycling of materials and a flow of energy Landscape = A region that includes several ecosystems Biosphere = All regions of earth’s land, water, and atmosphere in which life exists

5. Energy • The capacity to do work • Expressed in units of work (kilojoules, kJ) or units of heat energy (kilocalories, kcal) • Types: • potential energy – stored energy • kinetic energy – energy of motion

6. Potential vs. Kinetic Energy • potential energy – stored energy • a drawn bow, a stretched rubber band, a rock on top of a hill, water stored behind a dam, food • kinetic energy – energy of motion • a shooting arrow, a speeding bullet, a moving automobile, a rock rolling down a hill

7. First Law of Thermodynamics • Energy is neither created nor destroyed, but may be converted from one form to another • The total energy of any system and its surroundings is constant

8. Second Law of Thermodynamics • Whenever energy is converted from one form to another, some useful energy is degraded to lower–quality, more dispersed energy. Also can be stated: entropy increases • Entropy is a measure of disorder; increased entropy means increased randomness or dispersion • Degraded energy generally in form of heat • Continual energy input is needed to maintain a system, and no process is 100% efficient • Ordered systems result (e.g., living systems), even though entropy increases

9. Photosynthesis The biological process in which light energy from the sun is captured and transformed into the chemical energy of sugar molecules 6 CO2 + 12 H2O + light energy C6H12O6 + 6 H2O + 6 O2

10. Cellular Respiration The biological process in which the chemical energy stored in food is released and made available to do work within cells of organisms C6H12O6 + 6 O2 + 6 H2O 6 CO2 + 12 H2O + energy

11. Producers, Consumers, and Decomposers • Producers are autotrophs that manufacture food that can be used for themselves and/or other organisms • Consumers are heterotrophs that use the bodies of other organisms as a source of food • Decomposers are detritovores which eat decaying organic material

12. Energy flow through Ecosystems • Producers convert sunlight energy to FOOD through the process of PHOTOSYNTHESIS • Each trophic level becomes FOOD for the next level • Dead bodies and excrement become FOOD for the decomposers • Organisms convert food to energy and release HEAT through the process of RESPIRATION

13. Food Web A more realistic view of energy flow, showing the complex of interconnected food chains in an ecosystem Environment, Fifth Edition /fig3.10

14. Ecological Pyramids • Graphically represent the relative energy going from one trophic level to the next • 3 types: - Pyramid of numbers - Pyramid of biomass - Pyramid of energy

15. Pyramid of Numbers • Shows the number of organisms at each trophic level in a given ecosystem Environment, Fourth Edition /fig4.12

16. Pyramid of Biomass • Shows the total biomass (amount of living material) at each successive trophic level • Note there is only a 10% transfer of biomass from one level to another Environment, Fourth Edition /fig4.13

17. Pyramid of Energy • Shows the energy content of the biomass at each trophic level Environment, Fourth Edition /fig4.14

18. Gross Primary Productivity Plant cellular respiration Net Primary Productivity = Productivity of Producers • GPP – Gross Primary Productivity The total amount of photosynthetic energy captured in a given period of time • NPP – Net Primary Productivity The amount of biomass found in excess of the plant’s needs, available for consumers

19. Review Objectives What Is Ecology?• Define ecology.• Distinguish among the following ecological levels: population, community, ecosystem, landscape, and biosphere. The Energy of Life• Define energy, and explain how it is related to work and to heat.• Use examples to contrast potential energy and kinetic energy.• State the first and second laws of thermodynamics, and discuss the implications of these laws as they relate to organisms.• Write summary reactions for photosynthesis and cellular respiration, and contrast these two biological processes. The Flow of Energy Through Ecosystems• Define energy flow, trophic level, and food web.• Summarize how energy flows through a food web, using producer, consumer, and decomposer in your explanation.• Describe typical pyramids of numbers, biomass, and energy.• Distinguish between gross primary productivity and net primary productivity, and discuss human impact on the latter.

20. Review Objectives • What Is Ecology?• Define ecology.• Distinguish among the following ecological levels: population, community, ecosystem, landscape, and biosphere. • The Energy of Life• Define energy, and explain how it is related to work and to heat.• Use examples to contrast potential energy and kinetic energy.• State the first and second laws of thermodynamics, and discuss the implications of these laws as they relate to organisms.• Write summary reactions for photosynthesis and cellular respiration, and contrast these two biological processes. • The Flow of Energy Through Ecosystems• Define energy flow, trophic level, and food web.• Summarize how energy flows through a food web, using producer, consumer, and decomposer in your explanation.• Describe typical pyramids of numbers, biomass, and energy.• Distinguish between gross primary productivity and net primary productivity, and discuss human impact on the latter.